This invention relates to an air/fuel injector and control for an internal combustion engine.
In order to improve the performance of an internal combustion engine and particularly its fuel economy and exhaust emission control, it has been proposed to employ direct cylinder fuel injection. It has further been proposed to improve the atomization or disbursement of the fuel supply to the combustion chamber by the injector by also injecting high pressure air along with the fuel. The types of fuel air injectors which have been proposed employ a chamber or a plurality of chambers to which air and fuel are supplied under pressure and which are delivered to the combustion chamber when the injector valve is opened. In one form of control strategy, the fuel is all supplied to its respective chamber before the injector valve is opened. In another form of strategy, the fuel is supplied to the chamber during the time when the injector valve is opened. These types of charging strategies, however, present certain difficulties.
With the precharged type of injector, not all of the fuel may be discharged from its chamber when the injector valve is opened. This results in poor combustion and uneven combustion. The non-precharged type of fuel/air injector, on the other hand, does not present this problem but with this type of injector as well as the precharged type, it may be difficult to supply all of the required fuel to the combustion chamber without other problems.
For example, when running at high speed and high load conditions, a substantial amount of fuel is required. If this fuel must all be charged into the chamber of the fuel injector and then into the combustion chamber during the time when the injector valve is opened, it may not be possible to supply sufficient fuel or, alternatively, the amount of fuel supplied may be so great that full evacuation of the injector chamber and disbursement of the fuel is not possible. In addition, the duration of opening of the injector valve becomes so great that bouncing of the valve can be a problem.
A bouncing condition results when the injector valve is closed. The rapid closure of the injector valve tends to cause the valve to again bounce open until its motion is fully dampened and thus additional fuel may be delivered to the combustion chamber of the engine after the valve is closed. When this occurs, the fuel may actually be delivered at the time the spark plug is fired and this can give rise to misfiring, pre-ignition and other problems.
The problems aforedescribed are particularly acute in conjunction with two cycle crankcase compression engines. With such engines, as is well known, there is a substantial overlap between the closing of the exhaust port and the opening of the scavenge port and if the duration of fuel injection is too long, fuel may be discharged directly out of the exhaust port resulting in poor fuel economy and high exhaust gas emissions, particularly with unburned hydrocarbons.
It is, therefore, a principal object of this invention to provide an improved fuel injector and control for an internal combustion engine wherein adequate amounts of fuel can be delivered to the combustion chamber and fully disbursed without the fear of unburned fuel being discharged from the exhaust port of the engine. It is a further object of this invention to provide an improved air/fuel injector and control therefore wherein adequate amounts of fuel can be supplied to the engine under all running conditions without causing pre-ignition or other combustion difficulties.
It is a further object of this invention to provide an air/fuel injector and control for an engine wherein the dynamic range of operation of the fuel injector and the operation through this range is significantly improved.